Depinning, Ordering and Melting of Vortex Matter in Mesoscopic Channels
- Event time: 1:00pm
- Event date: 26th April 2004
- Speaker: Rut Besseling (Formerly School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
Vortex arrays in superconductors have received a great deal of attention as model system for studying frictional, depinning, dynamic ordering and melting phenomena of lattices driven through a random potential. In this talk I first give a short introduction to 'vortex physics', highlighting similarities and differences with colloidal systems. Then I discuss our studies on a system where vortices are confined to mesoscopic channels and flow along the pinning (shear) potential provided by static, disordered vortex arrays in the channel edges. On changing the magnetic field (overall vortex density) the arrays inside the channels undergo a series of transitions from n to n±1 vortex rows. These transitions and the varying mismatch of the arrays can be directly traced via Mode-Locking features in the dc stress-velocity curves, which appear on combined dc-rf driving. The flow stress exhibits maxima for mismatching structures. This is caused by a traffic jam-like mechanism arising from the quenched positional disorder in the confining arrays. Additionally, the sensitivity of Mode-Locking to plasticity/melting of the moving array allows to map the dynamic phase boundaries between coherent, plastic and fluid flow as function of magnetic field (mismatch) and temperature. The data provide evidence for an additional 'shaking temperature' generated by motion along the quenched, random potential. Magnetic and Superconducting Materials, University of Leiden. N. Kokubo et al Phys. Rev. Lett.88 247004 (2002) R. Besseling et al. Phys. Rev. Lett. 91 177002 (2003)
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..